I used to have to update these manually so did a bit of digging and found a few different tutorials that helped me slap this together. Now the year in your SMF footer copyright, the message always displays the current year.
Open index.template.php and find:
<div id="footer_section"><div class="frame">
<li class="copyright">', theme_copyright(), '</li>
$time = time () ;
echo ' <li>Copyright © ' . $year . ' YOUR-FORUM-NAME | All Rights Reserved</li>';